During maneuvering, significant somatic perceptions are available to pilots of tactical aircraft and are induced by the inertial acceleration reaction on the pilot's body and the coupling existing between the body and the actual aircraft seat. Such maneuvering often carries the aircraft close to the bounds of its flight envelope and exposes the pilot to a broad range of vibratory information concerning aircraft dynamic state as well as configuration. It is well known that pilots employ these perceptions in the handling of their aircraft. Consequently, in the art of aircraft simulators an effort has been made to develop devices which provide a rendition of these cues in the simulation of tactical aircraft.
The first major development in the art was the motion system. Motion systems, however, are limited in their ability to provide sustained acceleration information due to the excursion and velocity constraints intrinsic to the system. For high performance tactical aircraft simulators this limitation is particularly apparent. For such simulators, motion systems provide only the leading edge of the simulated acceleration. This is followed by a fading of the perception during the subliminal "washout" phase, during which the motion system restores itself to regain the capability expended in delivering the onset cue.
To supplement the information provided by motion systems and provide sustained acceleration cues, the "G-seat" was developed. The G-seat directly addresses the haptic-somatic sensory system, which consists of the muscle, joint, and flesh pressure receptors employed in perceiving physiological changes due to sustained acceleration.
Early G-seats were crude, employing such expedients as harnesses to move the pilot about in his seat, air cushions and the like. These early devices typically suffered from such serious shortcomings as seat cushion balooning, generation of false and conflicting cues, and deterioration of cockpit realism due to cumbersome extraneous hardware.
To overcome the problems associated with these prior art devices the present inventor, in conjunction with two co-workers previously devised a revolutionary new seat for simulating aircraft motion, described in U.S. Pat. No. 3,983,640, which issued Oct. 5, 1976. This invention, denominated an Advanced G Seat, provides compatible body excursion, flesh pressure gradient and area of contact cues associated with various acceleration profiles, while maintaining cockpit fidelity. At the heart of the invention are two mosaics of air cells having individual rigid top plates which define a seat pan surface and backrest surface. By individually driving each cell, the composite elevation, attitude and shape of these surfaces can be varied to provide the desired motion cues. A plurality of dynamic clam-shell shaped air cells are located on either side of the seat pan, to provide thigh pressure and area of contact cues. Also provided is a driven lap belt to supply ventral area pressure variation.
The versatility provided by the Advanced G Seat mosaic surface allows controlled variations in seat pan heave or sink, pitch, roll, contouring and, by way of the active clam-shell aircells, area of flesh contact. Also provided are backrest cushion translation, attitude reorientation (tip and tilt) and contouring. The surface shape, or contour variations provide the pilot with localized pressure change sensations on his body, corresponding, e.g., to his being pushed into the seat during high acceleration.
Three other G-seat related patents have issued since the Advanced G Seat, covering an auxiliary skin tension cueing system for use in conjunction with a G-seat (U.S. Pat. No. 4,030,207), a separate seat vibrator for the simulation of aircraft buffeting (U.S. Pat. No. 4,030,208) and another G-seat configuration (U.S. Pat. No. 4,059,909). The last patent, which issued to the instant inventor, employs a mosaic of separately driven air cells which make up the seat pan and backrest and which, as in the Advanced G Seat, provide a variable seat surface. Seat firmness cues are provided by a plurality of inflatable firmness cells which overlie the mosaic of aircells. These firmness cells provide firmness cues either by being inflated or, when used in conjunction with rigid plates located beneath them, by being deflated to lower the body onto the hard surface.
Each of the above g seats inventions is an extremely significant milestone in terms of mid-range g-level cueing, particularly the Advanced G Seat which has been employed in a number of tactical aircraft simulators with considerable success.
However the performance of g-seats employing the above inventions has been less than totally satisfactory. Because of the mosaic construction and separate motion of each element, the potential exists, under minimum maintenance conditions for nonsynchronous cell movement. Further, the range of localized pressure sensation available is fairly small, thus limiting the dynamic range of simulated g-loading. The result is an attenuated, possibly distorted perception of the g loading desired to be simulated.
Another limitation of the above prior art g-seats is that they have low element response bandwidths, typically of the order of 1 hertz or so. Because of this low bandwidth, it is impossible for these pneumatic g-seats to pass high frequency acceleration cues such as aircraft buffet without employing a separate "shaker" type device such as that disclosed in U.S. Pat. No. 4,030,207 mentioned above. Furthermore, in the absence of a platform motion system whose principal purpose is to track and reproduce the leading edge of an acceleration profile, it is almost impossible to use low bandwidth pneumatic g-seats to present faithful onset cues on a tactical aircraft simulator.
The seat system of the present invention provides highly improved subjective "feel" of the g-loading effects being simulated. Very strong localized pressure sensations are provided, greatly expanding the dynamic range of perceived g loading, while at the same time the seat feels like an integrated structure. Fewer driven elements are employed while band pass is increased to 10 hertz or more thus providing onset cueing capability. Further, buffeting cues can be provided directly by way of the seat system thus eliminating the need for a separate shaker system. These improvements are accomplished while at the same time retaining the compatible cue generation capability and cockpit fidelity which characterized the first generation g-seats.